1. Field of the Invention
The present invention relates to an insulator apparatus for vacuum insulating tubing.
More particularly, the present invention relates to an insulator apparatus for vacuum insulating tubing adapted to provide insulation at joints in a vacuum insulating tubing string including an insulating member and a joint protector surrounding and holding the member in place at the joints.
2. Description of the Related Art
In the petroleum industry, production tubing is disposed within a borehole for transporting oil and gas from subsurface bearing formations to the surface. This tubing is comprised of elongate sections threaded together to form a production string, the joint thereby formed being referred to variously as a tool joint, coupling, or upset.
In conjunction with this production tubing, it is frequently necessary to provide a system for delivering fluid media downhole. One reason may be to permit the injection of chemical treatment fluids near the producing formation for enhancing the production, for treatment of downhole conditions such as those involving undesirable corrosion, salt, or scale, and for delivery of corrosion or scale inhibitors, de-emulsifiers, or the like, downhole.
Yet another reason for providing these fluid delivery systems is for the transmission of fluid pressure to various downhole valves or tools from the surface for purposes of control or the like. Thus, various forms of injection or control lines referred to hereinafter generally as tubing and having internal diameters much smaller than that of the production tubing itself are provided which are disposed radially outward of and adjacent to the production tubing. In some cases the tubing is of an encapsulated variety wherein both the tubing and wire rope (which provides crush resistance from side forces) are encapsulated in an appropriate thermoplastic elastomer, whereas in other applications, the tubing may be of an unencapsulated or bare variety.
In other situations, electrical cables are routed downhole in like manner to the tubing for monitoring pressure instruments or for providing power for downhole motors or the like.
One problem with these tool joints and the associated tubing or cables (referred to hereinafter as tubing for convenience) is that they are frequently subjected to damage from contact with surrounding casing or the formation itself, such as when the production string is moved up or down within the borehole. This damage may be due to abrasion or compressive forces against the joint or tubing which often occurs as the tool joint is moved across a deviation in the borehole. Thus, means were sought for protecting this bare or unencapsulated tubing, cable and the tool joints from damage.
In deep water drilling operations, one difficulty in producing oil from such deep wells is the loss of heat associated with the oil as it flows out of the productive formation into the production tubing resulting in proportional increase in fluid viscosity and reduced well productivity. One answer to this vexing problem was the advent of vacuum insulated tubing, which provides a vacuum break between the production tubing and the outside world, greatly reducing heat loss as the productive fluid is communicated to the surface. However, heat loss is still a problem at the joints of the tubing where, out of necessity, the joints are not insulated and therefore heat can flow out of the joints to the surrounding.
Thus, there is a need in the art for an apparatus that can be attached to at the joints of vacuum insulated tubing insulating the joints from the outside world, while providing a protected conduit for production communication cables or other production wirelines.